The short answer
Check the air filter often on dusty trips, look at the oils after water crossings, keep the coolant and brake fluid in good condition, and shorten intervals for hard use. Always use the grades in your manual, and ask your dealer what severe-use service they recommend.
Do
- Check the air filter after every dusty trip
- Look at diff and transfer oils after water
- Keep coolant and brake fluid within their dates
- Use the oil grade in your manual
- Ask about severe-use intervals
Do not
- Run a clogged air filter
- Ignore milky or burnt-smelling oil
- Top up with random fluids
- Stretch intervals after hard use
- Blow a paper filter out with a hard air jet
Fluids
| Fluid | What hard use does | What to do |
|---|---|---|
| Engine oil and filter | Dust, heat and long low-range crawling age it faster. | Use the grade in your manual, and shorten the interval after hard use. Ask your dealer about severe service. |
| Coolant | Slow, hot work stresses the system, and old coolant protects less. | Check the level and strength, and keep the radiator clear of mud and grass. |
| Brake fluid | It absorbs moisture over time, and water crossings and long descents heat it. | Replace it on the schedule, and sooner if the pedal feels soft. |
| Diff and transfer case oil | Water can enter through the breathers, and it turns the oil milky. | Check after crossings, and change it if it looks milky or smells burnt. |
| Gearbox oil | Heat and load wear it. | Follow your manual. Ask about severe-use intervals if you crawl in low range a lot. |
Use the grades in your manual. Different oils suit different engines and conditions, and your manual or dealer is the right place to confirm them.
Filters
| Filter | Why it matters | What to do |
|---|---|---|
| Air filter | Dust and sand clog it, which chokes the engine and wastes fuel. | Check it after every dusty trip. Replace it when it is dirty or wet. |
| Fuel filter | Dirty fuel from remote pumps can clog it. | Replace it on the schedule, and sooner if you suspect bad fuel. |
| Cabin filter | Dust fills it, and the air conditioning suffers. | Check it after dusty trips, and replace it when it is dirty. |
| Oil filter | It collects what the oil carries. | Change it with every oil change. |
Do not blast a paper air filter with a hard air jet, because it can tear it. Tap it gently or replace it. Carry a spare air filter on dusty trips.
Checks by condition
- Dusty trips: air filter, cabin filter, radiator fins and engine oil
- Water crossings: diff, transfer case and gearbox oils, and the air filter
- Long climbs and low range: coolant, engine oil and the temperature gauge
- Long descents: brake fluid and pad wear. See brakes and wheel bearings
Keep a log
Write down every oil change, filter change and top-up with the date and the odometer reading. A log shows when hard use has shortened the interval, and it helps at a service and when you sell the car.
Pick the conditions
Tap the conditions to see what to check.
Tap conditions (6 to try)
Check first after Dusty trails
- Check first
- -
- Details
- -
Common mistakes
- Running a clogged air filter. It chokes the engine.
- Ignoring milky oil. It means water got in.
- Using the wrong grade. Follow the manual.
- Blowing a paper filter out hard. It can tear.
- Stretching intervals after hard use. Hard use ages fluids faster.
- Never keeping a log. You cannot see the pattern.
A final word. Fluid and filter needs depend on the car and the use. This guide is general information, not a specification. Use the grades and intervals in your owner's manual, and ask your dealer for severe-use advice.